Cracks along sector boundaries

Hi all, I'm new to Doomworld and to Doom map editing, so please forgive me if this question is n00balicious.

I'm using Doom Builder 1.68 and am trying to get a radiating light from the corner of a room, so I start off splitting the sector into bands:


At this point, there's no problem. I then use the Curve Lindef function (or just add vertices and draw a rough, manual curve] and get something like this:


Now, in the 3D preview, there are cracks along the floor where the sectors join...


...but when I playtest (ZDoom 2.1.5), everything looks fine. I'm guessing it's just a peculiarity with Doom Builder, but I'm worried in case I'm building incorrectly and leaving myself open to future problems with this map.

Any hints?

No, you're fine. 3D mode creates little visual distortions that 99% percent of the time will look and be just fine while playing.

That's exactly what I wanted to hear. Thanks! ^^

By the way, that's looking pretty good, and you're doing well.